Расчет флагов

for 8-bit add/adc, sub/sbc (it's similar with 16-bit opcodes) A=accumulator d=data to be added/subtracted, excluding carry flag r=result after calculation

carry: simply A>r for add, A<r for sub (or if r>8bit: r>>8&1) half carry: like you said it's (r^A^d)&0x10 overflow: ((A^r)&(d^r))>>5&4 for add, ((A^d)&(A^r))>>5&4 for sub